Drilling platforms are used to support equipment for drilling a well or borehole to a subterranean resource, such as oil or gas. The drilling platform may be onshore or offshore depending on the location of the desired subterranean resource. The drilling platform may include a derrick, tower, or other equipment support structure. A hoisting system may be coupled to the derrick and used for raising and lowering equipment, such as tubulars, drill strings, work strings, tools, drill bits, blowout preventers and other drilling and well components. Referring to FIG. 1, a drilling or well system 10 includes a floating vessel 12. In some embodiments, the floating vessel 12 is a drillship, a semi-submersible, or other floating structure. In other embodiments, the drilling system 10 is onshore or land based and the structure 12 may include pillars, columns, or other support members coupled to the ground. The drilling system 10 includes a derrick 14 constructed on a drill floor 26 of the vessel 12. In some embodiments, the derrick 14 is a tower or other drilling support structure. The drilling system 10 also includes a hoisting system 30 that interacts with the derrick 14 to raise and lower equipment with respect to the drill floor 26, which facilitates well drilling and completion operations.
The hoisting system 30 supports a drill string 18, which is suspended from a top drive 16 or other type of lifting device. The top drive 16 is coupled to a hoisting line (or lines) 20. The hoisting line 20 is passed over a sheave or sheaves in a crown block 24. The hoisting line is coupled to a rotatable drum in a drawworks 22 located on the drill floor 26 with the derrick 14. In some embodiment, the drawworks 22 includes or is replaced with other types of hoisting devices, such as a cylinder driven hoisting system. The drawworks 22 can reel in and reel out the hoisting line 20 over the rotatable sheave in the crown block 24 such that the top drive 16 and the drill string 18 are raised and lowered along a well center WC.